“It’s going to be the hardest moment for many Americans in their entire lives, and we really need to understand that if we want to flatten that curve and get through to the other side, everyone needs to do their part.”

Adams’s thoughts were echoed by Dr Anthony Fauci, the country’s foremost infectious diseases expert, in a White House briefing on Sunday. “This is probably going to be a very bad week,” Fauci said.

Donald Trump echoed similar language from the White House briefing room on Sunday, saying that the coming week would be difficult. The president said, however, there’s “a light at the end of the tunnel”.

“We are feeling confident in the days ahead America will endure the peak of this terrible pandemic,” he said. “Our warriors in this life and death battle are the incredible doctors and nurses and health care workers on the frontline of the fight.”

In Sunday’s press conference, Trump also repeatedly encouraged Americans to try hydroxychloroquine to treat coronavirus, despite a lack of scientific evidence to support the use of the anti-malaria drug as a possible remedy for Covid-19. Trump said his administration has ordered 29m doses to be distributed across the United States, and later on prevented Fauci from answering a question on the efficacy of the treatment from the White House podium.

Trump also said in the conference that Fema is airlifting supplies to affected states, including millions of masks, gloves, and sterile gowns.

He also took the opportunity to take digs at the governor of Illinois, CNN and a reporter from the Associated Press, calling CNN “fake news” for asking about the efficacy of hydroxychloroquine and scolding the AP reporter for asking “wise guy questions”.

New York state, the worst hit by far, recorded 594 deaths on Saturday – down from 630 deaths the day before, the first day-on-day decrease since the pandemic took off.

“The apex could be a plateau, and we could be on that plateau now,” New York governor Andrew Cuomo said, adding that the coming days would make clear which direction the state was headed. Overall 4,159 New Yorkers have died and there have been 122,031 confirmed cases, Cuomo said.

From Louisiana, a developing hotspot, Governor John Bel Edwards reiterated that his state was projected to run out of ventilators by Thursday and would reach intensive-care capacity two days after that.

As of Sunday, 477 people had died from Covid-19 in Louisiana, with well over half in the New Orleans metro area. New Orleans now has the highest per capita death rate of any city in the US, according to data analysis by the University of Louisiana at Lafayette.

“This is a tough emergency and it’s not different here than it is elsewhere,” Edwards told CNN’s State of the Union, confirming that 200 ventilators had arrived from the national stockpile on Saturday.

On Monday, Louisiana will open its first makeshift field hospital, at the Morial Convention Center in New Orleans. It will house 1,000 beds and, like other temporary sites in New York and elsewhere, is designed to ease the burden on city hospitals.

Senior infectious disease doctors, speaking to the Guardian last week, confirmed that hospitals in New Orleans have begun discussing the ethics of how to ration care should they become overwhelmed with Covid-19 patients.

As the crisis accelerates, five states have declined to issue stay-at-home orders: Iowa, Nebraska, North Dakota, South Dakota and Arkansas. All have Republican governors.

On Sunday, Arkansas governor Asa Hutchinson said there was no point issuing such an order because it would be ignored. “You have a stay-at-home order, tomorrow 600,000 Arkansans will still go to work,” Hutchinson said on NBC.

Fauci said states without stay-at-home orders were “putting themselves at risk”.

“I will not say we have it under control, that would be a false statement,” Fauci told CBS’s Face the Nation. “We are struggling to get it under control, and that’s the issue that’s at hand right now.” He said the rate of increase in new cases was slowing, an encouraging sign.

Adams, the surgeon general, urged people to stay at home no matter what rules are in place in their state.

“Ninety percent of Americans are doing their part, even in the states where they haven’t had a shelter in place [order],” Adams said. “But if you can’t give us 30 days, governors, give us a week, give us what you can, so that we don’t overwhelm our healthcare systems over this next week. And then let’s reassess at that point.”

Reaching again for imagery from the second world war, he added: “We want everyone to understand you’ve got to be Rosie the Riveter. You’ve got to do your part.”

Adams also advised people to wear masks or otherwise cover their mouths and noses when out in public, in addition to staying six feet apart.

“You need to make sure you’re not substituting social distancing with face masks,” he said.

Trump, 73, said again on Sunday in the press conference he would not wear a mask despite such federal guidelines. “I’m not going to wear one,” he said. “I would wear it if I thought it was important.”

His prospective opponent in the November election, Joe Biden, 77, said on Sunday he would wear a mask if he left his home in Wilmington, Delaware.

“Look, I think it’s important to follow the science, listen to the experts, do what they tell you,” Biden said. “[Trump] may not like how he looks in a mask but the truth of the matter is that – follow the science. That’s what they’re telling us.”